bacterial upper respiratory tract infections Flashcards
strep pyogenes
gram + cocci, chains
catalase - (no bubbling)
beta hemolytic
bacitracin sensitive, PYR +
staphylococci
catalase + (bubbling)
tells apart from strep pyogenes
how strep presents
pharyngitis, pyoderma, impetigo, erysipelas, cellulitis, necrotizing fasciitis, strep toxic shock
30% of sore throats in kids is caused by
group A strep - pharyngitis
signs of strep pharyngitis
petechiae in soft palate
inflammation in oropharynx
symptoms can inlude: nausea, vomiting, abdominal pan
strep pyogenes and rheumatic heart disease
M protein, antiphagocytic on outer surface of group A strep –> triggers anti-cardiac Ab responsible for leaflet thickening and deposits and RHD
MOLECULAR MIMICRY
haemophilus influenzae
gram - coccobacilli
curved ends on round rods
requires X AND V growth factors (both present in chocolate agar)
oxidase +
what are the growth requirements of haemophilus influenzae
requires X AND V growth factors (both present in chocolate agar)
x is hemin/heat stable; V is Nad or nadp/heat labile
grows best in 5-10% co2
types of h influenzae
6 capsular types a-f
type b are responsible for human diseases (primarily children)
nonencapsulated are normal flora in URT
which type of h influenzae causes disease in humans?
type b capsular
polyribose-ribitol phosphate (PRP or Hib) capsule is antiphagocytic
what protects from type b h influenzae?
antibody against PRP (polyribose ribitol phosphate) capsule
type b h infuenzae diseases
mostly affects nonvaccinated children
meningitis
epiglottitis
pneumonia
nonencapsulated h influenzae infections
acute atitis media and sinusitis——second to s pneumoniae
exaccerbations of COPD
conjunctivitis (daycare centers)
bacteremia/invasive infections in adults with underlying conditions
type b h influenzae usually infects who in the developed world?
nonvaccinated young children or elderly
how do anti-capsular antibodies protect humans?
they act as opsonins and mediate complement-dependent phagocytosis of the bacteria
Ab + complement can lead to bacterial lysis
how to treat h influenzae infections?
cephalosporin or ampicillin
Hib vaccinations for kids
what causes diptheria?
corynebacterium diphtheriae
cornuebacterium jeikeium causes
infections in immunosuppressed and is frequently resistant to many antibiotics
signs of diphtheria
incubation period 2-5 days
involves mucus membranes
classified by site (anterior nasal, tonsillar, laryngeal, ocular, genital, etc…)
how diphtheria progresses
enters URT
colonizes mucosa
makes diphtheria toxin –> toxin gene inhibits protein synthesis
can cause myocarditis, neuritis, or necrosis
creates pseudomembrane after necrosis and then death by obstruction
treatment for diphtheria
antitoxin - horse origin
antibiotic - kills bacteria BUT does not prevent intoxication
immunize with toxoid
what bacteria has M protein virulence factor
group a streptococci pyogenes
gram + rods that form chinese letters, non motile, non spore forming
catalase +
c diphtheriae
how does c diphtheriae toxin work?
A-B single chain toxin that ADP-ribosylates EF-2 and stops protein synthesis
cytotoxic to cells
